Test apparatus and testing method

1. A testing apparatus that tests a device under test, comprising:

a command executing unit operable to sequentially execute commands included in a test program for the device under test every command cycle;

a test pattern memory operable to store pattern sequence and pattern length identifying information corresponding to each of the commands, the pattern length identifying information identifying a pattern length of a test pattern sequence that is output during a command cycle period for executing each command;

a test pattern memory reading unit operable to read a test pattern sequence having a length corresponding to the pattern length identifying information stored on said test pattern memory in association with one command from said test pattern memory when the one command is executed; and

a test pattern outputting unit operable to output the test pattern sequence read by said test pattern memory reading unit in association with the one command to a terminal of the device under test during a command cycle period for executing the one command.

2. The testing apparatus as claimed in claim 1 , wherein

the testing apparatus tests the device under test by either slow mode having a short pattern sequence to be output when executing one command or a fast mode having a long pattern sequence in comparison to the slow mode,

said test pattern memory stores operation mode instructing information showing which one of the slow mode and the fast mode operates the testing apparatus during a cycle period for executing the command as the pattern length identifying information corresponding to each command, and

said test pattern outputting unit sequentially outputs each pattern of the test pattern sequence read by said test pattern memory reading unit to the terminal of the device under test according to a speed corresponding to the operation mode instructing information.

3. The testing apparatus as claimed in claim 2 , further comprising:

a slow mode format controlling unit operable to memorize a test pattern sequence of the fast mode outputting a pattern waveform identical with a test pattern sequence of the slow mode in association with each test pattern sequence of the slow mode,

wherein said test pattern outputting unit outputs the test pattern sequence of the fast mode memorized by said slow mode format controlling unit in association with the test pattern sequence of the slow mode to the terminal of the device under test when the test pattern sequence of the slow mode has been read corresponding to the one command.

4. The testing apparatus as claimed in claim 3 , further comprising:

a hold point register operable to set a hold point showing a retention period for holding the last logical value in a cycle just before outputting the test pattern sequence in the slow mode when the test pattern sequence is output in the slow mode,

wherein said slow mode format controlling unit outputs the last logical value in the cycle just before the output for the retention period and starts outputting the test pattern sequence read by said test pattern memory reading unit after a lapse of the retention period.

5. The testing apparatus as claimed in claim 3 , wherein said slow mode format controlling unit memorizes either of a data 0 pattern sequence outputting a logical value zero after outputting a logical value one for a predetermined period, a data 1 pattern sequence outputting the logical value one after outputting the logical value zero for the predetermined period, a negative pulse outputting the logical value zero for the predetermined period and again outputting the logical value one after outputting the logical value one for the predetermined period, or a positive pulse outputting the logical value one for the predetermined period and again outputting the logical value zero after outputting the logical value zero for the predetermined period.

6. The testing apparatus as claimed in claim 3 , wherein

said test pattern memory stores the test pattern sequence of the slow mode or the test pattern sequence of the fast mode that is output during a command cycle period executing the command in association with each command,

said slow mode format controlling unit converts the test pattern sequence of the slow mode read by said test pattern memory reading unit into the test pattern sequence of the fast mode outputting the pattern waveform designated by the test pattern sequence of the slow mode,

the testing apparatus further comprises a test pattern sequence selecting unit operable to select the test pattern sequence read by said test pattern memory reading unit or the test pattern sequence converted by said slow mode format controlling unit based on the pattern length identifying information corresponding to the read test pattern sequence, and

said test pattern outputting unit serially outputs the test pattern sequence selected by said test pattern sequence selecting unit to the terminal of the device under test.

7. The testing apparatus as claimed in claim 2 , wherein said test pattern outputting unit outputs the test pattern sequence of the slow mode to a scan input terminal of the device under test in advance of a test of the device under test in order to initialize the device under test in the test, and outputs the test pattern sequence of the fast mode in order to test the device under test.

8. A testing apparatus that tests a device under test, comprising:

a command executing unit operable to sequentially execute commands included in a test program for the device under test every command cycle;

an expectation pattern memory operable to store an expectation pattern sequence and pattern length indentifying information corresponding to each of the commands, the pattern length indentifying information identifying a pattern length of the expectation pattern sequence that is to be output sequentially compared with a plurality of output patterns sequentially output from a terminal of the device under test during a command cycle period for executing each command;

an expectation pattern memory reading unit operable to read an expectation pattern sequence having a length corresponding to the pattern length identifying information stored on said expectation pattern memory in association with one command from said expectation pattern memory when the one command is executed; and

an expectation comparing unit operable to compare the expectation pattern sequence read by said expectation pattern memory reading unit in association with the one command and an output pattern sequence consisting of the plurality of output patterns output from the terminal of the device under test, during a command cycle period executing the one command.

9. A testing method testing a device under test, comprising:

sequentially executing commands included in a test program for the device under test every command cycle;

storing in a pattern memory a test pattern sequence and pattern length identifying information corresponding to each of the commands, the pattern length indentifying information identifying a pattern length of the test pattern sequence that is output during a command cycle period for executing each command;

reading a test pattern sequence having a length corresponding to the pattern length identifying information stored on the test pattern memory in association with one command from the test pattern memory when the one command is executed; and

outputting the test pattern sequence read in said reading in association with the one command to a terminal of the device under test during a command cycle period for executing the one command.

10. A testing method testing a device under test, comprising:

sequentially executing commands included in a test program for the device under test every command cycle;

storing an expectation pattern memory an expectation pattern sequence and pattern identifying informatin corresponding to each of the commands, the pattern length identifying information identifying a pattern length of the expectation pattern sequence that is to be sequentially compared with a plurality of output patterns sequentially output from a terminal of the device under test during a command cycle period for executing each command;

reading an expectation pattern sequence having a length corresponding to the pattern length identifying information stored on the expectation pattern memory in association with one command from the expectation pattern memory when the one command is executed; and

comparing an expectation pattern sequence read in said reading in association with the one command and an output pattern sequence consisting of the plurality of output patterns output from the terminal of the device under test, during a command cycle period executing the one command.